Solid state battery and method of manufacturing solid state battery

ABSTRACT

A solid state battery that includes: a battery element including a positive electrode layer, a negative electrode layer, and a solid electrolyte layer interposed between the positive electrode layer and the negative electrode layer; a composite protective layer covering the battery element, wherein the composite protective layer includes a first protective layer and a second protective layer arranged around the battery element so as to have an overlapping region where the first protective layer and the second protective layer overlap each other; and a conducting part capable of extracting electricity from the battery element to an outside of the solid state battery, the conducting part extending from the overlapping region to the outside of the solid state battery.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of International applicationNo. PCT/JP2021/022373, filed Jun. 11, 2021, which claims priority toJapanese Patent Application No. 2020-103335, filed Jun. 15, 2020, theentire contents of each of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a solid state battery and a method ofmanufacturing the same.

BACKGROUND OF THE INVENTION

Conventionally, secondary batteries that can be repeatedly charged anddischarged have been used for various purposes. For example, thesecondary battery is used as a power supply of an electronic device suchas a smartphone or a notebook computer.

In the secondary battery, a liquid electrolyte (electrolytic solution)such as an organic solvent has been conventionally used as a medium formoving ions. However, the secondary battery using the electrolyticsolution has a problem such as leakage of the electrolytic solution.Therefore, a solid state battery including a solid electrolyte insteadof a liquid electrolyte has been developed.

Patent Document 1: Japanese Patent Application Laid-Open No. 2017-117696

Patent Document 2: Japanese Patent Application Laid-Open No. 2016-58142

Patent Document 3: Japanese Patent Application Laid-Open No. 2015-220099

SUMMARY OF THE INVENTION

In such a solid state battery, from the viewpoint of avoidingdeterioration of battery characteristics, it is required to takemeasures for preventing water vapor in the air from entering the inside.

The present invention has been made in view of such circumstances. Thatis, a main object of the present invention is to provide a solid statebattery capable of suitably suppressing entry of water vapor into theinside, and a method of manufacturing the solid state battery.

That is, in an embodiment of the present invention, provided is a solidstate battery including: a battery element including a positiveelectrode layer, a negative electrode layer, and a solid electrolytelayer interposed between the positive electrode layer and the negativeelectrode layer; a composite protective layer covering the batteryelement, wherein the composite protective layer includes a firstprotective layer and a second protective layer arranged around thebattery element so as to have an overlapping region where the firstprotective layer and the second protective layer overlap each other; anda conducting part capable of extracting electricity from the batteryelement to an outside of the solid state battery, the conducting partextending from the overlapping region to the outside of the solid statebattery.

Furthermore, in an embodiment of the present invention, provided is amethod of manufacturing a solid state battery, the method including:covering a first part of a battery element with a first protectivelayer, the battery element including a positive electrode layer, anegative electrode layer, and a solid electrolyte layer interposedbetween the positive electrode layer and the negative electrode layer;covering a second part of the battery element with a second protectivelayer so as to form an overlapping region in which the first protectivelayer and the second protective layer overlap each other; and providinga conducting part capable of extracting electricity from the batteryelement to an outside of the solid state battery, the conducting partextending from the overlapping region to the outside of the solid statebattery.

According to an embodiment of the present invention, entry of watervapor into the inside can be suitably suppressed.

BRIEF EXPLANATION OF THE DRAWINGS

FIG. 1 is a sectional view schematically illustrating a solid statebattery according to an embodiment of the present invention.

FIG. 2 is a sectional view schematically illustrating an aspect ofpreventing entry of water vapor by the solid state battery according toan embodiment of the present invention.

FIG. 3 is a sectional view schematically illustrating the solid statebattery according to an embodiment of the present invention.

FIG. 4 is a perspective view schematically illustrating the solid statebattery according to an embodiment of the present invention.

FIG. 5 is a sectional view schematically illustrating the solid statebattery (expanded state) according to an embodiment of the presentinvention.

FIG. 6 is a sectional view schematically illustrating the solid statebattery according to an embodiment (with a sealant) of the presentinvention.

FIG. 7 is a sectional view schematically illustrating a solid statebattery according to another embodiment of the present invention.

FIG. 8 is a sectional view schematically illustrating the solid statebattery according to another embodiment of the present invention.

FIG. 9 is a schematic diagram illustrating steps of manufacturing thesolid state battery according to an embodiment of the present invention.

FIG. 10 is a sectional view schematically illustrating a conventionalsolid state battery.

FIG. 11 is a perspective view schematically illustrating a conventionalsolid state battery.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the “solid state battery” of the present invention will bedescribed in detail. Although the description will be made withreference to the drawings as necessary, the illustrated contents areonly schematically and exemplarily illustrated for the understanding ofthe present invention, and the appearance, the dimensional ratio, andthe like may be different from the actual ones.

The “solid state battery” referred to in the present invention refers toa battery whose constituent elements are composed of a solid in a broadsense, and refers to an all-solid state battery whose batteryconstituent elements (particularly preferably all battery constituentelements) are composed of a solid in a narrow sense. In a preferredaspect, the solid state battery in the present invention is a laminatedsolid state battery configured such that layers constituting a batteryconstituent unit are laminated with each other, and preferably, suchlayers may be composed of a sintered body. Note that the “solid statebattery” includes not only a so-called “secondary battery” capable ofrepeating charging and discharging but also a “primary battery” capableof only discharging. According to a preferred aspect of the presentinvention, the “solid state battery” is a secondary battery. The“secondary battery” is not excessively limited by its name, and mayinclude, for example, a power storage device and the like.

The term “sectional view” as used in the present specification refers toa state when viewed from a direction substantially perpendicular to athickness direction of a battery element constituting the solid statebattery. An “up-down direction” and a “left-right direction” useddirectly or indirectly in the present specification correspond to anup-down direction and a left-right direction in the drawings,respectively. Unless otherwise specified, the same reference symbols orsigns indicate the same members or parts or the same semantic contents.In a preferred aspect, it can be understood that a downward direction ina vertical direction (that is, a direction in which gravity acts)corresponds to a “downward direction”, and an opposite directioncorresponds to an “upward direction”.

[Basic Configuration of Solid State Battery]

The solid state battery includes at least electrode layers of a positiveelectrode and a negative electrode and a solid electrolyte.Specifically, the solid state battery includes a battery elementincluding a battery constituent unit including a positive electrodelayer, a negative electrode layer, and a solid electrolyte interposedtherebetween.

In the solid state battery, each layer constituting the solid statebattery may be formed by firing, and the positive electrode layer, thenegative electrode layer, the solid electrolyte, and the like may form asintered layer. Preferably, the positive electrode layer, the negativeelectrode layer, and the solid electrolyte are each fired integrallywith each other, and therefore the battery element preferably forms anintegrally sintered body.

The positive electrode layer is an electrode layer containing at least apositive electrode active material. The positive electrode layer mayfurther contain a solid electrolyte. For example, the positive electrodelayer is composed of a sintered body containing at least positiveelectrode active material particles and solid electrolyte particles. Ina preferred aspect, the positive electrode layer is composed of asintered body substantially containing only positive electrode activematerial particles and solid electrolyte particles. On the other hand,the negative electrode layer is an electrode layer containing at least anegative electrode active material. The negative electrode layer mayfurther contain a solid electrolyte. For example, the negative electrodelayer is composed of a sintered body containing at least negativeelectrode active material particles and solid electrolyte particles. Ina preferred aspect, the negative electrode layer is composed of asintered body substantially containing only negative electrode activematerial particles and solid electrolyte particles.

The positive electrode active material and the negative electrode activematerial are substances involved in the transfer of electrons in thesolid state battery. Ions move (are conducted) between the positiveelectrode layer and the negative electrode layer via the solidelectrolyte, and electrons are transferred, whereby charging anddischarging are performed. The positive electrode layer and the negativeelectrode layer are particularly preferably layers capable of occludingand releasing lithium ions or sodium ions. That is, the solid statebattery is preferably an all-solid state secondary battery in whichlithium ions or sodium ions move between the positive electrode layerand the negative electrode layer via the solid electrolyte to charge anddischarge the battery.

(Positive Electrode Active Material)

Examples of the positive electrode active material contained in thepositive electrode layer include at least one selected from the groupconsisting of a lithium-containing phosphate compound having aNaSICON-type structure, a lithium-containing phosphate compound havingan olivine-type structure, a lithium-containing layered oxide, alithium-containing oxide having a spinel-type structure, and the like.Examples of the lithium-containing phosphate compound having aNaSICON-type structure include Li₃V₂(PO₄)₃. Examples of thelithium-containing phosphate compound having an olivine-type structureinclude Li₃Fe₂(PO₄)₃, LiFePO₄, and/or LiMnPO₄. Examples of thelithium-containing layered oxide include LiCoO₂ andLiCo_(⅓)Ni_(⅓)Mn_(⅓)O₂. Examples of the lithium-containing oxide havinga spinel-type structure include LiMn₂O₄ and/or LiNi_(0.5)Mn_(1.5)O₄.

Furthermore, examples of the positive electrode active material capableof occluding and releasing sodium ions include at least one selectedfrom the group consisting of a sodium-containing phosphate compoundhaving a NaSICON-type structure, a sodium-containing phosphate compoundhaving an olivine-type structure, a sodium-containing layered oxide, asodium-containing oxide having a spinel-type structure, and the like.

(Negative Electrode Active Material)

Examples of the negative electrode active material contained in thenegative electrode layer include at least one selected from the groupconsisting of an oxide containing at least one element selected from thegroup consisting of Ti, Si, Sn, Cr, Fe, Nb, and Mo, a carbon materialsuch as graphite, a graphite-lithium compound, a lithium alloy, alithium-containing phosphate compound having a NaSICON-type structure, alithium-containing phosphate compound having an olivine-type structure,and a lithium-containing oxide having a spinel-type structure. Examplesof the lithium alloy include Li—Al. Examples of the lithium-containingphosphate compound having a NaSICON-type structure include Li₃V₂(PO₄)₃and/or LiTi₂(PO₄)₃. Examples of the lithium-containing phosphatecompound having an olivine-type structure include Li₃Fe₂(PO₄)₃ and/orLiCuPO₄. Examples of the lithium-containing oxide having a spinel-typestructure include Li₄Ti₅O₁₂.

Furthermore, examples of the negative electrode active material capableof occluding and releasing sodium ions include at least one selectedfrom the group consisting of a sodium-containing phosphate compoundhaving a NaSICON-type structure, a sodium-containing phosphate compoundhaving an olivine-type structure, a sodium-containing oxide having aspinel-type structure, and the like. Note that, in the solid statebattery of the present invention according to a preferred aspect, thepositive electrode layer and the negative electrode layer may be made ofthe same material.

The positive electrode layer and/or the negative electrode layer maycontain a conductive material. Examples of the conductive materialcontained in the positive electrode layer and the negative electrodelayer include at least one kind of metal materials such as silver,palladium, gold, platinum, aluminum, copper, and nickel, and carbon, andthe like.

Moreover, the positive electrode layer and/or the negative electrodelayer may contain a sintering additive. Examples of the sinteringadditive include at least one selected from the group consisting oflithium oxide, sodium oxide, potassium oxide, boron oxide, siliconoxide, bismuth oxide, and phosphorus oxide.

Note that, in the solid state battery of the present invention accordingto a preferred aspect, the positive electrode layer and the negativeelectrode layer are made of the same material. In the solid statebattery of the present invention, the positive electrode layer and thenegative electrode layer may be made of the same material (For example,in such a case, the positive electrode active material and the negativeelectrode active material may be the same kind.).

(Solid Electrolyte)

The solid electrolyte is a material capable of conducting lithium ions.In particular, the solid electrolyte constituting a battery constituentunit in the solid state battery forms a layer capable of conductinglithium ions between the positive electrode layer and the negativeelectrode layer. Note that the solid electrolyte may be provided atleast between the positive electrode layer and the negative electrodelayer. That is, the solid electrolyte may also exist around the positiveelectrode layer and/or the negative electrode layer so as to protrudefrom between the positive electrode layer and the negative electrodelayer. Specific examples of the solid electrolyte include alithium-containing phosphate compound having a NaSICON-type structure,an oxide having a perovskite structure, an oxide having a garnet-type orgarnet-type similar structure, and an oxide glass ceramic-based lithiumion conductor. Examples of the lithium-containing phosphate compoundhaving a NaSICON-type structure include Li_(x)M_(y)(PO₄)₃ (1≤x≤2, 1≤y≥2,and M is at least one selected from the group consisting of Ti, Ge, Al,Ga, and Zr.). Examples of the lithium-containing phosphate compoundhaving a NaSICON-type structure include Li_(1.2)Al_(0.2)Ti_(1.8)(PO₄)₃.Examples of the oxide having a perovskite structure includeLa_(0.55)Li_(0.35)TiO₃. Examples of the oxide having a garnet-type orgarnet-type similar structure include Li₇La₃Zr₂O₁₂. As the oxide glassceramic-based lithium ion conductor, for example, a phosphate compound(LATP) containing lithium, aluminum, and titanium as constituentelements, and a phosphate compound (LAGP) containing lithium, aluminum,and germanium as constituent elements can be used.

Furthermore, examples of the solid electrolyte capable of conductingsodium ions include a sodium-containing phosphate compound having aNaSICON-type structure, an oxide having a perovskite structure, and anoxide having a garnet-type or garnet-type similar structure. Examples ofthe sodium-containing phosphate compound having a NaSICON-type structureinclude Na_(x)M_(y)(PO₄)₃ (1≤x≤2, 1≤y≤2, and M is at least one selectedfrom the group consisting of Ti, Ge, Al, Ga, and Zr.).

The solid electrolyte may contain a sintering additive. The sinteringadditive contained in the solid electrolyte may be selected from, forexample, the same materials as the sintering additive that can becontained in the positive electrode layer or the negative electrodelayer.

A thickness of the solid electrolyte layer is not particularly limited,and may be, for example, 1 μm to 15 μm, particularly 1 μm to 5 μm.

(Positive Electrode Current Collecting Layer and Negative ElectrodeCurrent Collecting Layer)

The positive electrode layer and the negative electrode layer may eachinclude a positive electrode current collecting layer and a negativeelectrode current collecting layer. Each of the positive electrodecurrent collecting layer and the negative electrode current collectinglayer may have a form of a foil, but may have a form of a sintered bodyfrom the viewpoint of reducing the manufacturing cost of the solid statebattery by integral firing and reducing the internal resistance of thesolid state battery. As a positive electrode current collectorconstituting the positive electrode current collecting layer and anegative electrode current collector constituting the negative electrodecurrent collecting layer, it is preferable to use a material having highconductivity, and for example, it is preferable to use silver,palladium, gold, platinum, aluminum, copper, nickel, or the like. Inparticular, copper is preferable because it hardly reacts with thepositive electrode active material, the negative electrode activematerial, and the solid electrolyte material, and has an effect ofreducing the internal resistance of the solid state battery. Note that,when the positive electrode current collecting layer and the negativeelectrode current collecting layer have the form of a sintered body, thepositive electrode current collecting layer and the negative electrodecurrent collecting layer may be formed of a sintered body containing aconductive material and a sintering additive. The conductive materialcontained in the positive electrode current collecting layer and thenegative electrode current collecting layer may be selected from, forexample, the same material as the conductive material that can becontained in the positive electrode layer and the negative electrodelayer. The sintering additive contained in the positive electrodecurrent collecting layer and the negative electrode current collectinglayer may be selected from, for example, the same material as thesintering additive that can be contained in the positive electrode layeror the negative electrode layer. Note that, in the solid state battery,the positive electrode current collecting layer and the negativeelectrode current collecting layer are not essential, and a solid statebattery in which such a positive electrode current collecting layer anda negative electrode current collecting layer are not provided is alsoconceivable. That is, the solid state battery in the present inventionmay be a solid state battery without the current collecting layer.

Thicknesses of the positive electrode layer and the negative electrodelayer are not particularly limited, but may be, for example, 2 μm to 50μm, particularly 5 μm to 30 μm, independently of each other.

The solid state battery, in particular the battery element, is generallyprovided with terminals (e.g. external electrodes). In particular, anend face electrode is provided on a side face of the battery element.More specifically, a positive-electrode-side end face electrodeconnected to the positive electrode layer and a negative-electrode-sideend face electrode connected to the negative electrode layer areprovided. Such end face electrodes preferably contain a material havinghigh conductivity. A specific material of the end face electrodes is notparticularly limited, but may be at least one selected from the groupconsisting of silver, gold, platinum, aluminum, copper, tin, and nickel.Furthermore, a terminal called a tab lead for extracting generatedelectricity to the outside is provided at an end part of each of the endface electrodes. The material of the tab lead is preferably a materialhaving a high electrical conductivity as with the end face electrode. Aspecific material of the tab lead is not particularly limited, but maybe at least one selected from the group consisting of silver, gold,platinum, aluminum, copper, tin, and nickel.

(Protective Layer)

The protective layer may be generally formed on an outermost side of thesolid state battery, and is for electrical, physical, and/or chemicalprotection. The material constituting the protective layer is preferablyexcellent in insulation property, durability and/or moisture resistance,and environmentally safe. For example, it is preferable to use glass,ceramics, a thermosetting resin and/or a photocurable resin.

[Characteristic Parts of the Present Invention]

Hereinafter, characteristic parts of the present invention will bedescribed.

The inventors of the present application have intensively studied asolution for enabling suppression of entry of water vapor into thebattery. As a result, the present inventors have devised a solid statebattery according to an embodiment of the present invention having thefollowing characteristics.

FIG. 1 is a sectional view schematically illustrating a solid statebattery according to an embodiment of the present invention. FIG. 2 is asectional view schematically illustrating an aspect of preventing entryof water vapor by the solid state battery according to an embodiment ofthe present invention. FIG. 3 is a sectional view schematicallyillustrating the solid state battery according to an embodiment of thepresent invention. FIG. 4 is a perspective view schematicallyillustrating the solid state battery according to an embodiment of thepresent invention. FIG. 5 is a sectional view schematically illustratingthe solid state battery (expanded state) according to an embodiment ofthe present invention.

The solid state battery according to an embodiment of the presentinvention is characterized particularly in the protective layer amongthe constitution elements described in the section of [Basicconfiguration of solid state battery] above. Specifically, the solidstate battery 200 according to an embodiment of the present inventionincludes a battery element 100, a composite protective layer 10 coveringthe battery element 100, and a conducting part 20 capable of extractingelectricity from the battery element 100 to the outside.

The term “composite protective layer” as used in the presentspecification refers to a combination of two or more protective layers.The term “conducting part” as used in the present specification refersto a generic term for members that contribute to electrical extraction,such as an end face electrode 21 provided on the battery element 100 anda tab lead 22 connected to the end face electrode 21. That is, theconducting part 20 includes the end face electrode 21 provided on thebattery element 100 and the tab lead 22 connected to the end faceelectrode 21.

That is, in an embodiment of the present invention, the battery element100 is covered with the composite protective layer 10 formed bycombining two or more protective layers. In other words, the compositeprotective layer 10 surrounds the battery element 100. As an example, asillustrated in FIG. 1 , the composite protective layer 10 is composed offirst protective layer 11 and second protective layer 12. Moreover, inan embodiment of the present invention, an overlapping region 50 inwhich the first protective layer 11 and the second protective layer 12overlap each other is formed in the composite protective layer 10, andthe conducting part 20 is extended from the overlapping region 50 to theoutside.

Note that, for the overlapping region 50, a positional relationshipbetween the first protective layer 11 and the second protective layer 12is not particularly limited, and for example, the second protectivelayer 12 may be positioned outside the first protective layer 11, andthe first protective layer 11 may be positioned outside the secondprotective layer 12. The overlapping region 50 may be composed of morethan two protective layers. For example, in the mode illustrated in FIG.1 , the overlapping region 50 is configured by two layers of the firstprotective layer 11 and the second protective layer 12, but for example,the overlapping region may also be configured using a third protectivelayer and a fourth protective layer.

The term “overlapping region” used in the present specification refersto a region where the first protective layer 11 and the secondprotective layer 12 overlap each other in a broad sense, and refers to aregion where a part of the first protective layer 11 and a part of thesecond protective layer 12 overlap each other in a narrow sense. Theterm “overlapping each other” refers to a state where a principalsurface of one protective layer and a principal surface of the otherprotective layer face each other directly or adjacently. That is, when aresin, a metal, or the like is interposed between the principal surfaceof one protective layer and the principal surface of the otherprotective layer, it is regarded as “overlapping each other” in theabove state. The term “water vapor” as used in the present specificationis not particularly limited to water in a gaseous state, and includeswater in a liquid state and the like. That is, the term “water vapor” isused to broadly include matters related to water regardless of thephysical state. Therefore, the “water vapor” can also be referred to asmoisture or the like, and in particular, as the water in the liquidstate, dew condensation water in which water in a gaseous state iscondensed can also be included.

The term “extended” as used in the present specification means a statewhere at least a part of another independent component located in acertain component extends from the certain component to the outside, andat least a part of the other independent component is exposed to theoutside. That is, “the conducting part 20 is extended from theoverlapping region 50 of the composite protective layer 10 to theoutside” as used in the present specification indicates a state where apart of the conducting part 20 electrically connectable to the batteryelement 100 covered with the composite protective layer 10 is exposed tothe outside through between the first protective layer 11 and the secondprotective layer 12 forming the overlapping region 50 of the compositeprotective layer 10 as illustrated in FIG. 1 .

As illustrated in FIG. 1 , the first protective layer 11, which is aconstitution element of the composite protective layer 10, does not needto cover the whole battery element 100, and similarly, the secondprotective layer 12 does not need to cover the whole battery element100. Finally, the first protective layer 11 and the second protectivelayer 12 may be disposed so as to cover the whole battery element 100with the first protective layer 11 and the second protective layer 12.That is, the composite protective layer 10 may be finally disposed so asto cover the whole battery element 100. Furthermore, as illustrated inFIG. 1 , the overlapping region 50 can be formed such that a part of oneprotective layer and a part of the other protective layer cover eachother. In other words, the overlapping region 50 can be formed bylaminating a part of the first protective layer 11 and a part of thesecond protective layer 12 each other. A direction in which the firstand second protective layers are laminated in the overlapping region 50is a direction substantially perpendicular to a lamination direction ofa positive electrode layer 110, a negative electrode layer 120, and asolid electrolyte 130 in the battery element 100. Furthermore, adirection in which the conducting part 20 is extended from theoverlapping region 50 to the outside is substantially perpendicular tothe direction in which the first and second protective layers arelaminated in the overlapping region 50, and on the other hand, issubstantially parallel to the lamination direction of the positiveelectrode layer 110, the negative electrode layer 120, and the solidelectrolyte 130 of the battery element 100. By adopting such aconfiguration, as in the solid state battery 200 of FIG. 1 , the firstprotective layer 11 can be interposed between most of the tab lead 22constituting the conducting part 20 excluding a connection part with theend face electrode 21 and the battery element 100. In other words, thetab lead 22 can be connected to the end face electrode 21 while the tablead 22 and the battery element 100 are separated from each other by thefirst protective layer.

As described above, in the solid state battery 200 according to oneembodiment of the present invention, the conducting part 20 is extendedfrom the overlapping region 50 of the composite protective layer 10 tothe outside. With such a configuration, the following technical effectscan be achieved.

When water vapor enters the battery element, deterioration of batterycharacteristics may be caused. The entry of water vapor into the batteryelement can be suppressed by covering a periphery of the battery elementwith a protective layer as a water vapor transmission preventing layer.In this regard, as illustrated in FIGS. 10 and 11 , in a conventionalsolid state battery 200′, a single protective layer 13′ is configured tocover a battery element 100′ by one circumference in sectional view. Inorder to extract electricity from the battery element 100′ to theoutside, a tab lead 22′, which is a constitution element of a conductingpart, may be connected to the battery element 100′ across the protectivelayer 13′. In other words, the tab lead 22′ is configured to protrudeoutward across the protective layer 13′. In such a configuration, sincethe tab lead 22′ crosses the protective layer 13′, a minute gap isgenerated between the tab lead 22′ and the protective layer 13′, and thegap may be a passage through which water vapor passes from the outsideto the battery element 100′.

In this regard, in the solid state battery 200 according to anembodiment of the present invention, as illustrated in FIGS. 1 and 2 ,the conducting part 20 connected to the battery element 100 is extendedfrom the overlapping region 50 to the outside. Therefore, as comparedwith the conventional solid state battery 200′ covered with the singleprotective layer 13′ (That is, there is no overlapping region.), in theextending direction (longitudinal direction) of the overlapping region50 in sectional view, a path length from the outside of the battery tothe battery element 100 can be increased by a length of the overlappingregion 50. As a result, water vapor 40 can be favorably suppressed fromreaching the battery element 100 from the outside as compared with theconventional solid state battery 200′.

Furthermore, as can be seen from the above description, in theoverlapping region 50, one protective layer and the other protectivelayer overlap each other. That is, the overlapping region 50 is a regionincluding two or more protective layers. Therefore, a thickness of theoverlapping region 50 is thicker than a thickness of the compositeprotective layer 10 in other parts other than the overlapping region 50.This makes it possible to increase the thickness of the protective layerin the overlapping region 50 as compared with the conventional solidstate battery 200′ covered with the single protective layer 13′ (Thatis, there is no overlapping region.) in a thickness direction(transverse direction) of the overlapping region 50 in sectional view.Therefore, as compared with the conventional solid state battery 200′,it is possible to favorably suppress the water vapor 40 from reachingthe battery element 100 from the outside.

Note that the first protective layer 11 and the second protective layer12 constituting the composite protective layer 10 described above arepreferably laminate films. By using the laminate film, it is possible toreduce the thickness, weight, and space of the solid state battery. Amaterial of the laminate film is not particularly limited as long as itis generally used for a solid state battery. The laminate film is formedby bonding a foil-shaped metal and a sheet-shaped resin. For example,the laminate film includes a metal layer as an intermediate layer 11b/12 b, a first resin layer 11 a/12 a covering one surface of the metallayer, and a second resin layer 11 c/12 c covering the other surface ofthe metal layer. See FIG. 3 .

The metal constituting the metal layer that is the intermediate layer ofthe laminate film is not particularly limited as long as it can impartheat resistance, seal strength, and impact resistance. Examples of themetal constituting the metal layer include at least one selected fromthe group consisting of aluminum, copper, nickel, titanium, stainlesssteel, and the like. Preferable examples include aluminum and copperfrom the viewpoint of electrical conductivity. The form of the metallayer is not particularly limited, and may be, for example, afoil-shaped layer, a sheet-shaped layer, or a deposited layer.

The first resin layer covering the metal layer that is the intermediatelayer of the laminate film may include a resin capable of imparting anadhesive property. The resin is preferably one that can impartadhesiveness by thermal welding, and specific examples of a resinmaterial constituting the adhesive resin include at least one selectedfrom polypropylene-based resin, polyethylene terephthalate-based resin,nylon-based resin, polyamide-based resin, acrylic-based resin, and thelike.

The second resin layer covering the metal layer that is the intermediatelayer of the laminate film may include a resin that electrically,physically, and/or chemically protects the battery element.Specifically, a resin material constituting the resin is notparticularly limited, and examples thereof include at least one selectedfrom a polyethylene-based resin, a polypropylene-based resin, apolyethylene terephthalate-based resin, a polyamide-based resin, anacryl-based resin, and the like.

When these protective layers easily transmit water vapor (moisture, gas(carbon dioxide), and the like), the water vapor enters the inside ofthe battery element, and the positive electrode layer, the negativeelectrode layer, and the solid electrolyte layer suction and absorb thewater vapor, which may deteriorate battery performance. In view of theabove, a water vapor transmission rate of the protective layer in athickness direction may be, for example, less than 5.0×10⁻³ g/(m² day),preferably 0 to less than 5.0×10⁻³ g/(m²·day). Note that the “watervapor transmission rate” mentioned herein refers to a transmission rateobtained by an MA method under measurement conditions of 85° C. and 85%RH using a gas transmission rate measuring device of model WG-15Smanufactured by MORESCO Corporation.

Alternatively, a value of the water vapor transmission rate obtainedunder the measurement conditions of 40° C., 90% RH, and a differentialpressure of 1 atm using a gas transmission rate measuring device ofmodel GTms-1 manufactured by Advanced Riko Co., Ltd. may be less than1.0×10⁻³ g/(m²·day).

From the viewpoint of preventing water vapor from entering the batteryelement 100, the overlapping region 50 is preferably wide. Specifically,in sectional view, it is more preferable as a length of the overlappingregion along a longitudinal direction of the tab lead 22 is longer. Thelength of the overlapping region may be 10% or more, preferably 20% ormore, 30% or more, and more preferably 40% or more with respect to aheight of the battery element 100 (that is, a length from an uppersurface to a lower surface of the battery element 100). Furthermore,from the viewpoint of facilitating adjustment of the position and lengthof the conducting part 20 extended to the outside, the length of theoverlapping region may be 100% or less, preferably 90% or less, 80% orless, or 70% or less, and more preferably 60% or less, with respect tothe height of the battery element 100.

The solid state battery according to one embodiment of the presentinvention preferably adopts the following aspect.

In one aspect, the conducting part 20 is preferably provided so as to besandwiched between the first protective layer 11 and the secondprotective layer 12 constituting the composite protective layer 10 (seeFIGS. 1 to 5 and the like). Specifically, the first protective layer 11is in contact with the conducting part 20, and the second protectivelayer 12 is in contact with the conducting part 20. In this state, theconducting part 20 is sandwiched between the first protective layer 11and the second protective layer 12. In another aspect, as illustrated inFIG. 1 , the conducting part 20 may be provided between an outer surfaceof the first protective layer 11 and an inner surface of the secondprotective layer 12. In such a configuration, the conducting part 20 issandwiched between the first protective layer 11 and the secondprotective layer 12 so as to be substantially parallel to the firstprotective layer 11 and the second protective layer.

That is, it is preferable that the conducting part 20 is positionedbetween the first protective layer 11 and the second protective layer12, and the conducting part 20, the first protective layer 11, and thesecond protective layer 12 are integrated. By adopting such aconfiguration, since the protective layers are positioned on both sidesof the conducting part 20 in sectional view, the conducting part 20 canbe brought into surface contact with each other by the two protectivelayers, and a minute gap between the conducting part 20 and eachprotective layer can be suitably reduced. As a result, the water vaporcan be suitably suppressed from passing through the overlapping region50.

Note that, from the viewpoint of suppressing water vapor from passingthrough the overlapping region 50 on both the positive electrode sideand the negative electrode side, it is preferable that two overlappingregions 50 are provided in sectional view. Specifically, it ispreferable to provide one that sandwiches the conducting part on thepositive electrode side (corresponding to the tab lead 22) and one thatsandwiches the conducting part on the negative electrode side(corresponding to the tab lead 22).

In one aspect, the conducting part 20 and the composite protective layer10 are preferably provided along a contour surface of the batteryelement 100 (see FIGS. 1 to 8 and the like).

In the present specification, the “contour surface of the batteryelement 100” means a surface that defines the shape or appearance of thebattery element 100. In the present specification, “the conducting part20 and the composite protective layer 10 are provided along the contoursurface of the battery element 100” means a state where the conductingpart 20 and the composite protective layer 10 are provided substantiallyparallel to an extending direction of the contour surface of the batteryelement 100.

That is, it is preferable that the conducting part 20 and the compositeprotective layer 10 extend in substantially the same direction as theextending direction of the contour surface of the battery element 100.In the present specification, the “extending direction of the contoursurface of the battery element 100” means a direction in which thecontour surface advances in the longitudinal direction. The conductingpart 20 and the composite protective layer 10 only need to extend atleast at a glance in substantially the same direction as the extendingdirection of the contour surface of the battery element 100, and theconducting part 20 and the composite protective layer 10 do notnecessarily need to extend in exactly the same direction as theextending direction of the contour surface of the battery element 100.For example, due to a positional relationship among the conducting part20, the composite protective layer 10, and the battery element 100,there may be a part where a part of the conducting part 20 and a part ofthe composite protective layer 10 do not extend substantially in thesame direction and parallel to the extending direction of the contoursurface of the battery element 100.

In the conventional solid state battery 200′, as described above, thetab lead 22′, which is a constitution element of the conducting part, isconfigured to cross the protective layer 13′ and protrude toward theoutside. Therefore, an area required for mounting in the conventionalsolid state battery 200′ is further required by an area of the tab leadprotruding to the outside. Furthermore, since the tab lead is a partthat extracts electricity from the solid state battery and does notcontribute to power generation of the solid state battery, the tab leadcan lead to a decrease in power generation capacity per unit area of thesolid state battery according to the area of the protruding conductingpart.

In this regard, in an embodiment of the present invention, theconducting part 20 is extended from the overlapping region 50 where thefirst protective layer 11 and the second protective layer 12 overlapeach other. The overlapping region 50 is a constitution element of thecomposite protective layer 10 that covers the battery element 100, andthus may be generally in the form of a contour of the battery element100. Therefore, the conducting part 20 extended from the overlappingregion 50 can also have a structure in which the protrusion issuppressed along the contour of the battery element 100. Since theconducting part 20 (specifically, the tab lead 22) may have a structurealong the contour of the battery element 100 instead of the protrudingstructure, the solid state battery 200 according to an embodiment of thepresent invention can be surface-mounted on an electronic substrate as awhole.

In one aspect, it is preferable that an extended part (corresponding tothe tab lead 22) of the conducting part 20 to the outside includes abent part 20A (see FIGS. 2 to 5 and the like). The bent part hereinmeans a bent part. The form of bending is not particularly limited, andfor example, as illustrated in FIGS. 2 to 5 , the extended part of theconducting part 20 to the outside may be bent so as to have a rightangle part. Alternatively, the extended part to the outside of theconducting part 20 may be bent so as to have a part drawing an arc(curved shape), and specifically, may be bent along a surface of theprotective layer.

As illustrated in FIG. 2 , the extended part (corresponding to the tablead 22) of the conducting part 20 to the outside is connected to anelectronic substrate 300 or the like when the solid state battery 200according to an embodiment of the present invention is surface-mounted.At that time, the extended part (corresponding to the tab lead 22) ofthe conducting part 20 to the outside can be formed in a bent formaccording to a mounting area of the solid state battery 200 according toan embodiment of the present invention, a positional relationshipbetween the solid state battery 200 and the electronic substrate 300, orthe like, and a connection method between the solid state battery 200and the electronic substrate 300, or the like.

The length of the conducting part 20 extended to the outside is notparticularly limited as long as electricity can be taken out from theconducting part 20. From the viewpoint of suitable surface mounting ofthe solid state battery, the extended conducting part 20 is preferablyprovided such that an end part of the extended conducting part 20 isprovided on at least one of the upper surface side and the lower surfaceside of the battery element 100 covered with the first protective layer11 or the second protective layer 12. Specifically, it is preferablethat the end part of the conducting part 20 (specifically, the tab lead22) along the contour of the battery element 100 is provided on theupper surface side or the lower surface side of the solid state battery200, for example, the lower surface side. As a result, the solid statebatteries 200 can be mounted on the electronic substrate 300 in the samerow, and the overall surface mounting area can be further reduced.Furthermore, from the viewpoint of further reducing the overall surfacemounting area and more reliably achieving the surface mounting of thesolid state battery 200, it is preferable that at least a part of theextended part of the conducting part 20 is in “surface” contact with asurface of the electronic substrate 300. By making contact with the“surface”, a contact area between the conducting part 20 and theelectronic substrate 300 can be increased. As illustrated in FIG. 2 ,such a form can be achieved by providing a bent part in the extendedpart of the conducting part 20 such that at least a part of the extendedpart of the conducting part 20 to the outside is substantially parallelto the surface of the electronic substrate 300.

Note that the end part of the extended conducting part 20 is notnecessarily fixed to the first protective layer 11 or the secondprotective layer 12, and may be a free end at which the end part canfreely move. In this regard, from the viewpoint of reducing the mountingarea, in one aspect, a form in which at least the end part of theextended conducting part 20 is fixed to the first protective layer 11 orthe second protective layer 12 is preferable.

By adopting such a form, the end part of the extended conducting part 20is brought into close contact along the side surface of the batteryelement 100, and the close contact state can be maintained. Since thepart protruding from the solid state battery can be more reliablysuppressed, the mounting area can be reduced.

Moreover, since the close contact state is maintained, it is possible tosuitably prevent the end part of the extended conducting part 20 frombeing bent and deformed when a force is applied from the outside to theend part of the extended conducting part 20. As a result, the solidstate battery 200 can be appropriately surface-mounted on the electronicsubstrate 300.

A method of fixing the end part of the extended conducting part 20 tothe first protective layer 11 or the second protective layer 12 is notparticularly limited. In this regard, it is preferable to fix with anadhesive from the viewpoint of ease of fixing. The form of the adhesiveis, for example, liquid, paste, sheet, solid, or powder. The type of theadhesive is, for example, an aqueous adhesive, a chemical reactionadhesive, a solvent adhesive, or a hot melt adhesive. Examples of amaterial of the adhesive include at least one selected from the groupconsisting of a silicone-based resin, an acrylic-based resin, anepoxy-based resin, a urethane-based resin, and the like.

Furthermore, during charging and discharging of the solid state battery200, as ions move in the solid electrolyte layer between the positiveelectrode layer and the negative electrode layer, the active materialcontained in each electrode layer may expand and contract along thelamination direction. In particular, when the active material, that is,the electrode layer expands along the lamination direction, tensilestress acting in an upward direction and tensile stress acting in adownward direction are generated due to this. In this regard, accordingto the present aspect, when the solid state battery 200 issurface-mounted on the electronic substrate 300, a minute space can beprovided between the solid state battery 200 and the electronicsubstrate 300. The presence of such a space also makes it possible toreceive an expanding part of the solid state battery 200 due toexpansion of the electrode layer along the lamination direction (seeFIG. 5 ).

In one aspect, the overlapping region 50 is preferably provided along aside surface of the battery element 100. Preferably, it is providedalong the whole side surface of the battery element 100 (see FIGS. 2 to5 and the like). The term “side surface” as used in the presentspecification means a surface extending in a direction relativelyperpendicular to an upper surface or a lower surface among surfacesconstituting the battery element 100. As can be seen from the abovedescription, there are a plurality of the “side surfaces” depending onthe form of the battery element 100. Therefore, the term “overlappingregion is provided along the side surface of the battery element 100.”as used in the present invention means that the overlapping region isprovided with respect to a surface of the battery other than the uppersurface or the lower surface of the battery element 100.

With such a configuration, since the overlapping region 50 does notprotrude from the battery element 100, a mounting area required forsurface mounting is reduced. In particular, when the end part of theconducting part 20 (specifically, the tab lead 22) along the contour ofthe battery element 100 is provided on the upper surface side or thelower surface side of the solid state battery 200, for example, thelower surface side, a part other than the end part of the conductingpart 20 (specifically, the tab lead 22) can be accommodated in theoverlapping region 50 along the side surface of the battery element 100,and it is possible to suitably achieve both surface mounting of thesolid state battery 200 on the electronic substrate 300 and suppressionof entry of water vapor into the battery.

In one aspect, as illustrated in FIG. 6 , a sealant 24 is preferablyprovided in the conducting part 20 located in the overlapping region 50as necessary. FIG. 6 is a sectional view schematically illustrating thesolid state battery according to an embodiment (with a sealant) of thepresent invention.

Due to the presence of the sealant 24, the conducting part 20 located inthe overlapping region 50 and the two protective layers 11 and 12constituting the overlapping region 50 can be suitably bonded. As aresult, in the overlapping region 50, the conducting part 20 and the twoprotective layers 11 and 12 can be favorably adhered by surface insectional view, and a minute gap between the conducting part 20 and eachprotective layer can be more favorably reduced. As a result, the watervapor can be more suitably suppressed from passing through theoverlapping region 50.

A material of the sealant 24 is not particularly limited as long as theconducting part 20 located in the overlapping region 50 and the twoprotective layers 11 and 12 constituting the overlapping region 50 canbe suitably bonded, and examples thereof include at least one selectedfrom the group consisting of a polyethylene-based resin, apolypropylene-based resin, and a polyethylene terephthalate-based resin.

In one aspect, the first protective layer 11 and the second protectivelayer 12 include an aluminum foil 11 b and an aluminum foil 12 b asintermediate layers (see FIG. 3 ). When the battery element 100 iscovered with the first protective layer 11, the aluminum foil 11 b,which is an intermediate layer of the protective layer, is electricallyconnected to the end face electrode 21 on a positive electrode side andthe end face electrode 21 on a negative electrode side, and aninsulating material is preferably provided on the end face of theprotective layer from the viewpoint of preventing occurrence of a shortcircuit through the aluminum foil 11 b. The method of an insulationtreatment for providing the insulating material is not particularlylimited, and any method may be used as long as it contributes topreventing a short circuit of the battery element 100 via the protectivelayer.

Note that the positional relationship between the conducting part 20 andthe overlapping region 50 is not particularly limited untilconfirmation, and any structure may be used according to the form ofsurface mounting. For example, a structure as illustrated in FIGS. 7 and8 can be adopted. As an example, in the structure of FIG. 7 , theexposed parts of the conducting parts 20 on the positive electrode sideand the negative electrode side are positioned so as to face each otherwith the battery element 100 interposed therebetween. As a result, theconducting part 20 on the positive electrode side and the conductingpart 20 on the negative electrode side of the solid state battery 200are positioned to be more distant from each other, so that thepossibility that both electrodes are short-circuited can be reduced.Furthermore, as illustrated in FIG. 8 , the design of the overlappingregions on the positive electrode side and the negative electrode sideand the design of the tab lead 22 can be appropriately changedasymmetrically depending on a mounting destination of the solid statebattery 200. This enables flexible surface mounting according to asurface form of the surface mounting destination of the solid statebattery 200.

Furthermore, the thickness of the overlapping region 50 is determined bythe thicknesses of the first protective layer 11 and the secondprotective layer 12 forming the overlapping region.

The thickness of the first protective layer 11 is preferably 1 μm to 500μm, more preferably 2 μm to 300 μm, still more preferably 3 μm to 100μm, for example, 50 μm, from the viewpoint of suppressing deteriorationof battery performance due to entry of water vapor into the batteryelement.

The thickness of the second protective layer 12 is preferably 1 μm to500 μm, more preferably 2 μm to 300 μm, still more preferably 3 μm to100 μm, for example, 50 μm, from the viewpoint of suppressingdeterioration of battery performance due to entry of water vapor intothe battery element.

The overlapping region is preferably 2 μm to 1000 μm, more preferably 4μm to 600 μm, still more preferably 6 μm to 200 μm, for example, 100 μmfrom the viewpoint of further suppressing deterioration of batteryperformance due to entry of water vapor into the battery element.

[Method of Manufacturing Solid State Battery of Present Invention]

Hereinafter, a method of manufacturing a solid state battery accordingto an embodiment of the present invention will be described. The methodof manufacturing a solid state battery according to an embodiment of thepresent invention roughly includes the following steps (i) to (iv) inorder (see FIGS. 9(a) to 9(h).). Specifically, a method of manufacturinga solid state battery according to an embodiment of the presentinvention includes the steps of:

-   -   preparing the battery element 100 including the positive        electrode layer 110, the negative electrode layer 120, and the        solid electrolyte layer 130 interposed between the positive        electrode layer 110 and the negative electrode layer 120;    -   providing the first protective layer 11 to cover a part of the        battery element 100;    -   providing the conducting part 20 capable of extracting        electricity from the battery element 100 to the outside; and    -   providing the second protective layer 12 to cover a remaining        part other than the part of the battery element 100.

In particular, the method of manufacturing a solid state batteryaccording to an embodiment of the present invention is characterized inthat the overlapping region 50 in which the first protective layer 11and the second protective layer 12 overlap each other is formed, and thesecond protective layer 12 is provided so that the conducting part 20 isextended from the overlapping region 50 to the outside.

Hereinafter, steps of obtaining the solid state battery according to anembodiment of the present invention will be specifically described.

Hereinafter, for better understanding of the present invention, onemanufacturing method will be exemplified and described, but the presentinvention is not limited to this method. Furthermore, temporal matterssuch as the following description order are merely for convenience ofdescription, and are not necessarily limited thereto.

[Preparation of First Protective Layer]

First, as illustrated in FIG. 9(a), the first protective layer 11 isprepared.

[Deep drawing processing of laminate film]

Next, as illustrated in FIG. 9(b), a laminate film as the firstprotective layer 11 is subjected to drawing processing to be molded intoa shape covering the battery element 100. The drawing processing is notparticularly limited as long as it is a processing method in which thelaminate film is processed into a concave shape by applying pressure tothe laminate film and narrowing the laminate film to form a shape inwhich the laminate film covers the battery element 100. For example, alaminate film is placed on a box-shaped mold along the shape of thebattery element 100, and pressure is applied from above the laminatefilm by a mold imitating the shape of the battery element 100, therebymolding the first protective layer 11 covering the battery element 100.The present invention is not limited thereto, and the battery element100 may be pressed against the laminate film to perform drawingprocessing.

[Attachment of First Protective Layer 11]

Next, as illustrated in FIG. 9(c), the battery element 100 is insertedinto the first protective layer 11 obtained by the above method, and thefirst protective layer 11 is attached so as to cover the battery element100. Specifically, the first protective layer is covered such that apart of the upper surface or a part of the lower surface of the batteryelement 100 is exposed. In a preferred aspect, the first protectivelayer is attached so as to cover a surface other than the upper surfaceor the lower surface of the battery element 100. More specifically, thefirst protective layer 11 is attached such that the end face of thefirst protective layer is located at a boundary between the uppersurface and the side surface of the battery element 100. Note that it ispreferable to previously attach the end face electrode 21 to the sidesurface of the battery element 100.

The end face of the first protective layer 11 may be provided with aninsulating material 31 to prevent a short circuit of the battery element100. The insulating material 31 is not particularly limited as long asit has electrical insulation, and may be, for example, an insulatingresin. Examples of a material of the insulating resin include at leastone selected from the group consisting of an epoxy-based resin, anacrylic-based resin, a phenol-based resin, and a synthetic rubber.

[Attachment of Tab Lead 22]

Next, as illustrated in FIGS. 9(d) and 9(e), the tab lead 22 is attachedto the end face electrode 21 provided on the battery element 100 that isnot covered with the first protective layer 11. Preferably, a conductiveadhesive 23 is applied to the end part of the tab lead 22 by metal maskprinting, so that the end part of the tab lead 22 and the end faceelectrode 21 of the battery element 100 are attached to electricallyconnect to each other. The conductive adhesive 23 may be a conductivepaste, and is made of, for example, a resin material containing aconductive filler. Examples of the conductive filler include at leastone selected from the group consisting of nickel, copper, aluminum,gold, carbon, and the like, and examples of the resin material includeat least one selected from the group consisting of an epoxy-based resin,an acrylic-based resin, a silicone-based resin, a urethane-based resin,and the like.

Next, as illustrated in FIG. 9(f), the tab lead 22 is positioned alongthe contour surface of the side surface of the battery element 100 withthe end part of the tab lead 22 connected to the end face electrode 21of the battery element 100 as a base point. When the tab lead 22 isdisposed along the side of the battery element 100, the tab lead 22 maybe bent.

[Attachment of Second Protective Layer 12]

Next, as illustrated in FIG. 9(g), after the tab lead 22 is positionedso as to follow the contour surface of the side surface of the batteryelement 100, the second protective layer 12 is attached in a directionopposite to the direction in which the first protective layer 11 isattached. In other words, a surface of the second protective layer 12 isdisposed with respect to the surface of the battery element 100 that isnot covered with the first protective layer 11. Thereafter, the end partof the second protective layer 12 is disposed along the side surface ofthe battery element 100. At this time, since the end part of the firstprotective layer 11 is already disposed on the side surface of thebattery element 100, the overlapping region 50 in which the secondprotective layer 12 and the first protective layer 11 overlap is formed.Specifically, a layer in which the battery element 100, the firstprotective layer 11, the tab lead 22, and the second protective layer 12are arranged in this order is formed from the battery element 100 towardthe outside, and the tab lead 22 is extended from the overlapping region50. In other words, the conducting part 20 including the end faceelectrode 21 and the tab lead 22 is extended from the overlapping regionto the outside.

From the viewpoint of preventing water vapor from entering the batteryelement 100, it is preferable to bring the first protective layer 11located in the overlapping region 50, the tab lead 22 as a constitutionelement of the conducting part 20, and the second protective layer 12into a close contact state. The method of bringing into close contact isnot particularly limited, but can be brought into close contact bymechanical bonding, pressure bonding, welding, an adhesive, or the like.In a preferred aspect, from the viewpoint of more improving the closecontact state between the first protective layer 11, the tab lead 22,and the second protective layer 12, it is preferable that the sealant 24is applied to the tab lead 22 in advance, and the sealant 24 is providedto the overlapping region 50. For example, the sealant 24 may be made ofat least one resin material selected from the group consisting of apolyethylene-based resin, a polypropylene-based resin, an ethylene-vinylacetate copolymer-based resin, a polyamide-based resin, an acryl-basedresin, and the like.

[Fixing of Tab Lead 22]

Finally, as illustrated in FIG. 9(h), the tab lead 22 whose one end is afree end, that is, the end part (that is, the end part of the extendedconducting part 20) of the tab lead 22 which is not connected to thebattery element 100 is positioned along the contour surface of thebattery element 100. Specifically, the tab lead 22 is bent so as to bein contact with the first protective layer 11. At this time, an adhesiveor the like can be applied to a part where the tab lead 22 and the firstprotective layer 11 are in contact with each other to bond and fix thetab lead 22 and the first protective layer 11 to each other. As theadhesive, an adhesive as exemplified in [0062] can be used.

The solid state battery 200 according to an embodiment of the presentinvention can be finally obtained through such a step (FIG. 9(h)). Notethat the bending of the tab lead 22 and the adhesion fixation to thefirst protective layer in the [Fixing of tab lead 22] may be performed,for example, immediately before the solid state battery 200 of thepresent invention is surface-mounted on the electronic substrate 300.Specifically, after manufacturing until the state of FIG. 9(g) isobtained, the manufacturing may be temporarily stopped before theadhesive is applied, and the state of FIG. 9(g) may be temporarilystored. Design items such as presence or absence of bending of the tablead 22, a length of a part from which the tab lead 22 is extended, abonding and fixing position of the tab lead 22, a bending part, and abending direction may be appropriately determined according to a shapeand the like of the electronic substrate to be surface-mountedthereafter. By adopting such a step, the solid state battery 200 of thepresent invention can be flexibly surface-mounted according to the shapeof the electronic substrate.

In the finally obtained solid state battery 200 according to anembodiment of the present invention, the following operational effectscan be exhibited.

Specifically, in the obtained solid state battery 200 according to anembodiment of the present invention, the conducting part 20 connected tothe battery element 100 is extended from the overlapping region 50 tothe outside. Therefore, as compared with the conventional solid statebattery 200′ covered with the single protective layer 13′ (That is,there is no overlapping region.), in the extending direction(longitudinal direction) of the overlapping region 50 in sectional view,a path length from the outside of the battery to the battery element 100can be increased by a length of the overlapping region 50. As a result,water vapor 40 can be favorably suppressed from reaching the batteryelement 100 from the outside as compared with the conventional solidstate battery 200′.

Furthermore, as can be seen from the above description, in theoverlapping region 50, one protective layer and the other protectivelayer overlap each other. That is, the overlapping region 50 is a regionincluding two or more protective layers. Therefore, a thickness of theoverlapping region 50 is thicker than a thickness of the compositeprotective layer 10 in other parts other than the overlapping region 50.This makes it possible to increase the thickness of the protective layerin the overlapping region 50 as compared with the conventional solidstate battery 200′ covered with the single protective layer 13′ (Thatis, there is no overlapping region.) in a thickness direction(transverse direction) of the overlapping region 50 in sectional view.Therefore, as compared with the conventional solid state battery 200′,it is possible to favorably suppress the water vapor 40 from reachingthe battery element 100 from the outside.

Although one embodiment of the present invention has been describedabove, only typical examples of the application range of the presentinvention have been illustrated. Therefore, a person skilled in the artmay easily understand that the present invention is not limited thereto,and various modifications may be made.

The solid state battery according to an embodiment of the presentinvention can be used in various fields where battery use or powerstorage is assumed. Although it is merely an example, the solid statebattery according to an embodiment of the present invention can be usedin the fields of electricity, information and communication (mobiledevice fields such as, for example, mobile phones, smart phones,smartwatches, notebook computers and digital cameras, activity meters,arm computers, and electronic paper) in which mobile devices and thelike are used, home and small industrial applications (for example, thefields of electric tools, golf carts, and home, nursing, and industrialrobots), large industrial applications (for example, fields of forklift,elevator, and harbor crane), transportation system fields (for example,the field of hybrid vehicles, electric vehicles, buses, trains,power-assisted bicycles, electric two-wheeled vehicles, and the like),power system applications (for example, fields such as various types ofpower generation, road conditioners, smart grids, and household powerstorage systems), medical applications (medical equipment fields such asearphone hearing aids), pharmaceutical applications (fields such asdosage management systems), IoT fields, space and deep sea applications(for example, fields such as a space probe and a submersible), and thelike.

DESCRIPTION OF REFERENCE SYMBOLS

300: Electronic substrate

310: Electronic substrate connection part

200: Solid state battery

100: Battery element

110: Positive electrode layer

120: Negative electrode layer

130: Solid electrolyte layer

10: Composite protective layer

11: First protective layer

11 a: Protective film

11 b: Aluminum foil

11 c: Sealing film

12: Second protective layer

12 a: Protective film

12 b: Aluminum foil

12 c: Sealing film

13′: Protective layer

20: Conducting part

20A: Bent part

21: End face electrode

22, 22′: Tab lead

23: Conductive adhesive

24: Sealant

31: Insulating material

40: Water vapor

50: Overlapping region

1. A solid state battery comprising: a battery element including apositive electrode layer, a negative electrode layer, and a solidelectrolyte layer interposed between the positive electrode layer andthe negative electrode layer; a composite protective layer covering thebattery element, wherein the composite protective layer includes a firstprotective layer and a second protective layer arranged around thebattery element so as to have an overlapping region where the firstprotective layer and the second protective layer overlap each other; anda conducting part capable of extracting electricity from the batteryelement to an outside of the solid state battery, the conducting partextending from the overlapping region to the outside of the solid statebattery.
 2. The solid state battery according to claim 1, wherein theconducting part is sandwiched between the first protective layer and thesecond protective layer in the overlapping region.
 3. The solid statebattery according to claim 1, wherein the conducting part and thecomposite protective layer are located along a contour surface of thebattery element.
 4. The solid state battery according to claim 3,wherein the conducting part and the composite protective layer extend ina direction substantially identical with an extending direction of thecontour surface of the battery element.
 5. The solid state batteryaccording to claim 1, wherein the conducting part includes a bent partthat extends to the outside of the solid state battery.
 6. The solidstate battery according to claim 1, wherein the conducting part is incontact with each of the first protective layer and the secondprotective layer in the overlapping region.
 7. The solid state batteryaccording to claim 1, wherein the overlapping region is located along aside surface of the battery element.
 8. The solid state batteryaccording to claim 7, wherein the overlapping region is located along awhole side surface of the battery element.
 9. The solid state batteryaccording to claim 1, wherein a thickness of the composite protectivelayer in the overlapping region is greater than a thickness of thecomposite protective layer in a part other than the overlapping region.10. The solid state battery according to claim 1, further comprising asealant disposed in the conducting part in the overlapping region. 11.The solid state battery according to claim 1, wherein the firstprotective layer and the second protective layer face each other in theoverlapping region.
 12. The solid state battery according to claim 1,wherein at least an extended end part of the conducting part is locatedon at least one of an upper surface side and a lower surface side of thebattery element covered with the first protective layer or the secondprotective layer.
 13. The solid state battery according to claim 1,wherein at least an extended end part of the conducting part is bondedto the first protective layer or the second protective layer with anadhesive.
 14. The solid state battery according to claim 1, wherein thefirst protective directly covers the battery element, and the solidstate battery further comprises an insulating material on an end face ofthe first protective layer that electrically insulates the firstprotective layer and the battery element.
 15. The solid state batteryaccording to claim 1, wherein the first protective and the secondprotective layer are laminate films that include a metal intermediatelayer, a first resin layer covering a first surface of the metalintermediate layer, and a second resin layer covering a second surfaceof the metal intermediate layer.
 16. A method of manufacturing a solidstate battery, the method comprising: covering a first part of a batteryelement with a first protective layer, the battery element including apositive electrode layer, a negative electrode layer, and a solidelectrolyte layer interposed between the positive electrode layer andthe negative electrode layer; covering a second part of the batteryelement with a second protective layer so as to form an overlappingregion in which the first protective layer and the second protectivelayer overlap each other; and providing a conducting part capable ofextracting electricity from the battery element to an outside of thesolid state battery, the conducting part extending from the overlappingregion to the outside of the solid state battery.
 17. The method ofmanufacturing a solid state battery according to claim 16, wherein theconducting part is sandwiched between the first protective layer and thesecond protective layer in the overlapping region.
 18. The method ofmanufacturing a solid state battery according to claim 16, wherein theconducting part and a composite protective layer defined by the firstprotective layer and the second protective layer extend along a contoursurface of the battery element.
 19. The method of manufacturing a solidstate battery according to claim 18, wherein the conducting part and thecomposite protective layer extend in a direction substantially identicalwith an extending direction of the contour surface of the batteryelement.
 20. The method of manufacturing a solid state battery accordingto claim 18, wherein the conducting part includes an extended part thatis bent along the contour surface of the battery element to the outsideof the solid state battery.